Abstract: NO CHECK option for CREATE TABLE/ALTER TABLE
Q. What does the NO CHECK option do with ALTER/CREATE TABLE
A. NO CHECK allows you to create referential integrity without worrying weather existing data matches the referential integrity rule or not. Without NO CHECK, creation of referential integrity will fail if related records do exist in the referenced table.
Hopefully,this makes sense for ALTER TABLE, but why does CREATE TABLE have this option? The option is there for CREATE table simply because CREATE TABLE and ALTER TABLE have the same options. In reality, NO CHECK used in conjunction with CREATE TABLE does nothing because your table does not have any data yet.